For the evolved universal terrestrial radio access (E-UTRA) uplink (UL), there are several transmit power control (TPC) proposals that were submitted to third generation partnership project (3GPP) long term evolution (LTE) Work Group 1 (WG1). These proposals can be generally divided into (slow) open loop TPC and slow closed loop or channel quality information (CQI)-based TPC.
Open loop TPC is based on pathloss measurement and system parameters where the pathloss measurement is performed at a wireless transmit/receive unit (WTRU) and the system parameters are provided by an evolved Node-B (eNodeB).
Closed loop TPC is typically based on TPC feedback information, (such as a TPC command), that is periodically sent from the eNodeB where the feedback information is generally derived using signal-to-interference noise ratio (SINR) measured at the eNodeB.
Open loop TPC can compensate for long-term channel variations, (e.g. pathloss and shadowing), in an effective way, for instance, without the history of the transmit power. However, open loop TPC typically results in pathloss measurement errors and transmit power setting errors. On the other hand, slow closed loop or CQI-based TPC is less sensitive to errors in measurement and transmit power setting, because it is based on feedback signaled from the eNodeB. However, slow closed loop or CQI-based TPC degrades performance when there is no available feedback due to UL transmission pause, or pauses in the feedback transmission or channel variations are severely dynamic.
For the UL E-UTRA, there are several intra-cell PC proposals, which have been submitted to third generation partnership project (3GPP) long term evolution (LTE) work group (WG)#1. These proposals can be generally divided into slow open loop PC and slow closed loop, (or CQI based PC). Open loop PC can compensate for long-term channel variations, (e.g., pathloss and shadowing), in an effective way, for instance, without the history of the transmit power, but it typically suffers from errors in pathloss measurement and transmit power setting. On the other hand, slow closed loop or CQI based PC is less sensitive to errors in measurement and transmit power setting, because it is based on feedback signaled from the eNodeB. However, it degrades performance when there is no available feedback due to UL transmission pause or pauses in the feedback transmission.
As such there exists a need for an improved method of transmission power control.